This invention generally relates to a system for determining the position of an object relative to a robot. More particularly, this invention relates to a device and method for determining the location, orientation and configuration of an object relative to a robot.
Robots have many industrial uses. One challenge associated with all robot operations is ensuring that the robot performs the desired operation accurately. A typical operation requires accurately locating a workpiece relative to the robot so that the robot moves into appropriate positions to perform the desired operations. A variety of methods have been suggested for locating a workpiece relative to a robot.
One method of locating a work piece relative to a robot includes "touching off" on various selected points of the workpiece. Typically, a touch-sensitive device is supported on the robot arm and robot position information is recorded when the sensing device contacts the workpiece. The robot information is then used to determine the location of the workpiece relative to the robot. An example of this method is disclosed in U.S. Pat. No. 4,590,578.
While the conventional touch sensing operation is useful, it is not without drawbacks and is not adequate for all situations. Typical touch sensing operations require that the workpiece be placed in a fixed position relative to the robot throughout the locating procedure. This is required because the reference frame of the robot relative to the workpiece becomes meaningless if the workpiece moves relative to the robot between touches during the location procedure. In many instances, the size of the workpiece or the workpiece configuration does not permit the robot to accurately determine all of the needed position or configuration information while using the conventional technique. It often is necessary or desirable to move the workpiece into various positions and/or orientations relative to the robot during the location procedure. With conventional techniques, this cannot be accomplished.
This invention addresses the need for determining the position, orientation and/or configuration of a workpiece while allowing the workpiece to be reoriented relative to a robot during a touch sensing procedure. With this invention it becomes possible to move a workpiece relative to the robot throughout the locating procedure, which represents a substantial advantage compared to the conventional technique.